The present invention relates to a cassette discriminating apparatus suitable for use in magnetic recorders such as VHS video cassette recorders ("VHS" is the trademark of Victor Company of Japan, Ltd.).
The VHS video cassette recorders can be used with two types of cassettes. The cassettes of a first type include T-60, T-20, T-168, T-120, T-140, T-100 and T-80 cassettes whose supply and take-up reels have substantially the same hub diameter. These cassettes are used for both home video decks and so-called "camcorders" (integrated video camera and recorders). The cassettes of a second type include a TC-20 cassette, for example, and have a supply reel whose hub is larger in diameter than the hub of a take-up reel. The cassettes of the second type are used mainly for the camcorders.
The cassette of the second type is smaller (about one-third) in size than the cassette of the first type and, therefore, the use of the cassettes of the second type makes it possible to provide an extremely compact and lightweight video cassette recorder. Those video cassette recorders which are constructed for exclusive use with the second, small cassettes are unable to load the first, large cassette. However, it is possible to load the second, small cassette on a video cassette recorder which is basically constructed to load the first, large cassette. To this end, a full-size adaptor having the same size as the first cassette is prepared for permitting attachment of the second cassette. With a second, small cassette mounted thereon, the full-size adaptor is loaded on the standard video cassette recorder.
Since the adaptor containing the second, small cassette has the same size as the first, large cassette and is loaded in the same manner as the first, large cassette, the conventional video cassette recorders are unable to discriminate the cassette loaded thereon. With this impossibility of cassette discrimination, the tension on the magnetic tape is substantially uncontrolled. Consequently, the magnetic tape is likely to be damaged when used with the conventional video cassette recorder.